U.S. patent application number 15/989697 was filed with the patent office on 2019-11-28 for apparatus and method for coating specimens.
The applicant listed for this patent is Rolls-Royce High Temperature Composites Inc.. Invention is credited to Stephen Harris.
Application Number | 20190360097 15/989697 |
Document ID | / |
Family ID | 68613876 |
Filed Date | 2019-11-28 |
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United States Patent
Application |
20190360097 |
Kind Code |
A1 |
Harris; Stephen |
November 28, 2019 |
APPARATUS AND METHOD FOR COATING SPECIMENS
Abstract
An apparatus for coating specimens includes a reaction chamber
and a plurality of reaction modules in the reaction chamber for
containing specimens to be coated, where each reaction module
includes a module inlet and a module outlet. A plurality of
conduits are configured to be in fluid communication with at least
one gas source external to the reaction chamber, and each of the
conduits terminates in one of the reaction modules for delivery of
gaseous reagents to the specimens to be coated. The module outlets
are in fluid communication with the reaction chamber for expulsion
of gaseous reaction products from the reaction modules.
Inventors: |
Harris; Stephen; (Long
Beach, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rolls-Royce High Temperature Composites Inc. |
Cypress |
CA |
US |
|
|
Family ID: |
68613876 |
Appl. No.: |
15/989697 |
Filed: |
May 25, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/045 20130101;
C04B 2235/5244 20130101; C04B 35/62868 20130101; C04B 41/457
20130101; C23C 16/26 20130101; C04B 35/62873 20130101; C04B 35/806
20130101; C04B 41/87 20130101; C04B 2235/614 20130101; C23C
16/45559 20130101; C04B 35/565 20130101; C04B 41/455 20130101; C04B
41/85 20130101; C23C 16/325 20130101; C23C 16/342 20130101; C04B
35/62863 20130101; C04B 41/4531 20130101 |
International
Class: |
C23C 16/455 20060101
C23C016/455; C04B 41/85 20060101 C04B041/85; C04B 41/87 20060101
C04B041/87; C04B 41/45 20060101 C04B041/45; C23C 16/32 20060101
C23C016/32; C23C 16/34 20060101 C23C016/34; C23C 16/26 20060101
C23C016/26 |
Claims
1. An apparatus for coating specimens, the apparatus comprising: a
reaction chamber; a plurality of reaction modules in the reaction
chamber for containing specimens to be coated, each reaction module
including a module inlet and a module outlet; and a plurality of
conduits configured to be in fluid communication with at least one
gas source external to the reaction chamber, each of the conduits
terminating in one of the reaction modules for delivery of gaseous
reagents to the specimens to be coated, wherein the module outlets
are in fluid communication with the reaction chamber for expulsion
of gaseous reaction products from the reaction modules.
2. The apparatus of claim 1, further comprising one or more outlet
ports from the reaction chamber for removal of the gaseous reaction
products.
3. The apparatus of claim 1, further comprising one or more inlet
ports in the reaction chamber, wherein the conduits pass through
and/or are connected to the one or more inlet ports.
4. The apparatus of claim 1, further comprising a removable lid
secured to an end of the reaction chamber.
5. The apparatus of claim 1, wherein the reaction modules are
arranged adjacent to each other along a longitudinal axis of the
reaction chamber.
6. The apparatus of claim 5, wherein the two or more reaction
modules are stacked within the reaction chamber.
7. The apparatus of claim 6, wherein a first of the reaction
modules is stacked on a sample support plate, and wherein a second
of the reaction modules is stacked on the first of the reaction
modules, such that a top surface of the first of the reaction
modules functions as a sample support plate for the second of the
reaction modules.
8. The apparatus of claim 1, comprising from three to six reaction
modules.
9. The apparatus of claim 1, wherein the reaction modules are sized
to accommodate a single level of the specimens.
10. The apparatus of claim 1, wherein the reaction chamber has a
cylindrical shape, and wherein each of the reaction modules has a
cylindrical shape.
11. The apparatus of claim 1, wherein the reaction chamber and/or
each of the reaction modules comprise graphite or a carbon-carbon
composite.
12. A method for coating specimens, the method comprising: heating
a reaction chamber containing a plurality of reaction modules and a
plurality of specimens to be coated, each of the reaction modules
including a module inlet and a module outlet and containing at
least one of the specimens; flowing gaseous reagents through the
module inlets and into the reaction modules, the gaseous reagents
chemically reacting to form coatings on the specimens; and
maintaining a pressure in each of the reaction modules higher than
a pressure in the reaction chamber, gaseous reaction products
thereby being expelled from the reaction modules through the module
outlets.
13. The method of claim 12, wherein the reaction chamber comprises
one or more outlet ports, and wherein the gaseous reaction products
are removed from the reaction chamber through the one or more
outlet ports.
14. The method of claim 13, wherein the one or more outlet ports
are in fluid communication with a vacuum pump.
15. The method of claim 12, wherein the gaseous reagents are flowed
into the reaction modules through a plurality of conduits in fluid
communication with one or more gas sources, each of the conduits
terminating in one of the reaction modules.
16. The method of claim 15, wherein the conduits pass through
and/or are connected to one or more inlet ports in the reaction
chamber.
17. The method of claim 12, wherein the pressure in each of the
reaction modules is from about one to about five orders of
magnitude higher than that in the reaction chamber.
18. The method of claim 12, wherein the pressure in each of the
reaction modules is in a range from about 1 Torr to about 50 Torr,
and the pressure in the reaction chamber is in a range from about 1
mTorr to about 50 mTorr.
19. The method of claim 12, wherein the reaction chamber is heated
to an elevated temperature in a range from about 700.degree. C. to
about 1800.degree. C.
20. The method of claim 12, wherein the specimens comprise porous
specimens, and wherein the gaseous reagents flowed through the
module inlets infiltrate the porous specimens.
21. The method of claim 20, wherein the porous specimens comprise
silicon carbide fiber preforms, and wherein the coatings comprise
silicon carbide, boron nitride, or carbon.
Description
TECHNICAL FIELD
[0001] The present disclosure is related generally to an apparatus
and method for coating specimens.
BACKGROUND
[0002] Ceramic matrix composites have been identified as candidate
materials for components in the hot-section of jet engines due to
their high temperature capability, low weight, and low coefficient
of thermal expansion. In some instances these components are
manufactured by laying up stacked 2D cloth or using 3D laminates to
form a fiber preform, depositing a fiber-matrix interphase coating
and rigidizing the fiber preform through chemical vapor
infiltration (CVI), infiltrating the rigidized preform with a
ceramic slurry to form an impregnated preform, and melt
infiltrating the impregnated preform with molten silicon to render
the composite nearly fully dense.
[0003] When performing CVI in a conventional "batch style" reactor
100, such as that shown in FIG. 1, gradients in deposition rate may
occur throughout the reactor 100. This is particularly true when
comparing deposition rates between levels; reaction product gases
produced during deposition on the upstream levels can reverse bias
the deposition reactions on the downstream levels, thereby reducing
the deposition rate. An improved CVI method that reduces or
eliminates downstream contamination from reaction product gases and
improves the uniformity of the CVI process would be
advantageous.
BRIEF SUMMARY
[0004] An apparatus for coating specimens includes a reaction
chamber and a plurality of reaction modules in the reaction chamber
for containing specimens to be coated, where each reaction module
includes a module inlet and a module outlet. A plurality of
conduits are configured to be in fluid communication with at least
one gas source external to the reaction chamber, and each of the
conduits terminates in one of the reaction modules for delivery of
gaseous reagents to the specimens to be coated. The module outlets
are in fluid communication with the reaction chamber for expulsion
of gaseous reaction products from the reaction modules.
[0005] A method of coating specimens includes heating a reaction
chamber containing a plurality of reaction modules and a plurality
of specimens to be coated, where each of the reaction modules
includes a module inlet and a module outlet and contains at least
one of the specimens. Gaseous reagents are flowed through the
module inlets and into the reaction modules where they chemically
react to form coatings on the specimens. A pressure in each of the
reaction modules is higher than a pressure in the reaction chamber,
and thus gaseous reaction products are expelled from the reaction
modules through the module outlets and may be removed from the
reaction chamber through one or more outlet ports during
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows a cross-sectional schematic of a prior art
apparatus for chemical vapor infiltration.
[0007] FIG. 2 shows a cross-sectional schematic of one embodiment
of an improved apparatus for coating porous or nonporous
specimens.
DETAILED DESCRIPTION
[0008] A new apparatus for chemical vapor infiltration (CVI) of
porous specimens, such as ceramic fiber preforms, has been
developed. The apparatus may also be used to coat specimens using
chemical vapor deposition (CVD). The apparatus is designed to
reduce or eliminate downstream contamination from reaction product
gases, thereby allowing coatings to be uniformly deposited on a
number of specimens throughout the apparatus. A coating method that
may be carried out in the apparatus is also described below.
Components referred to as being "in fluid communication with" each
other in the description that follows are directly or indirectly
connected or otherwise related in such a way that fluid (e.g., a
gas) can flow between the components in one or both directions.
[0009] Referring to FIG. 2, the apparatus 200 includes a reaction
chamber 202 and a plurality of reaction modules 204 in the reaction
chamber 202 for containing specimens (e.g., porous specimens) 230
to be coated. Each reaction module 204 includes a module inlet 206
and a module outlet 208. The apparatus 200 also includes a
plurality of conduits 212 configured to be in fluid communication
with at least one gas source external to the apparatus 200. Each
conduit terminates in one of the reaction modules 204 for delivery
of gaseous reagents from the gas source to the specimens 230.
Exemplary flow paths of the gaseous reagents are represented by
shaded arrows in FIG. 2. Each conduit 212 extends through at least
one module inlet 206. A plurality of the conduits 212 may pass
through and/or be connected to one or more inlet ports 210 in the
reaction chamber 202.
[0010] As illustrated in FIG. 2, the apparatus 200 may include a
single inlet port 210 through which multiple conduits 212 pass. In
an alternative embodiment, the apparatus may include multiple inlet
ports, and a single conduit or multiple conduits may pass through
each inlet port. Each of the conduits 212 may either pass through
an inlet port 210 or have a downstream end secured to the inlet
port 210. In all of these embodiments, the conduits 212 are
configured to be in fluid communication with one or more gas
sources during operation of the apparatus 200 in order to supply
gaseous reagents into the reaction modules 204. In some
embodiments, additional conduits external to the reaction chamber
202 may connect the inlet port(s) to the gas source(s).
Accordingly, the conduits 212 may be directly or indirectly
connected with the one or more gas sources.
[0011] The module outlets 208 are in fluid communication with the
reaction chamber 202 and configured to direct gaseous reaction
products out of the reaction modules 204, e.g., toward an inner
wall of the reaction chamber 202 and/or in a direction transverse
to a longitudinal axis of the reaction chamber 202. Each reaction
module 204 includes one or more module outlets 208. Exemplary flow
paths of the gaseous reaction products are represented by unshaded
arrows in FIG. 2. Gaseous reaction products expelled from the
module outlets 208 may be removed from the reaction chamber 202
through one or more outlet ports 214, as shown for example in FIG.
2. During operation of the apparatus 200, the outlet port(s) 214
may be in fluid communication with a vacuum pump for providing a
reduced pressure in the reaction chamber 202 compared to the
reaction modules 204, as discussed below.
[0012] The apparatus 200 may further comprise a lid 218 secured to
an end of the reaction chamber 202. The one or more inlet ports 210
may be disposed in the lid 218, which may be removed from the
reaction chamber 202 as needed. The conduits 212 may also be
removed and reinserted as needed. For example, after use of the
apparatus 200, the lid 218 and/or conduits 212 may be readily
removed to allow access to the reaction chamber 202 for cleaning
and/or specimen removal. The reaction modules 204 may also be
individually removable from the reaction chamber 202 to facilitate
easy specimen insertion and removal. The reaction chamber 202 may
be sealed during operation to maintain a controlled environment
therein.
[0013] As shown in FIG. 2, the reaction modules 204 may be arranged
adjacent to each other along a longitudinal axis of the reaction
chamber 202. More particularly, the reaction modules 204 may be
(vertically) stacked within the reaction chamber 202. For example,
a first of the reaction modules 204a may be stacked on a sample
support plate 220, and a second of the reaction modules 204b may be
stacked on the first of the reaction modules 204a, such that a top
surface of the first of the reaction modules 204a functions as a
sample support plate for the second of the reaction modules 204b.
The number of reaction modules 204 included in the reaction chamber
202 typically ranges from three to six, although the chamber 202
may be designed to include a larger number (e.g., greater than six)
reaction modules 204. The reaction modules 204 may be sized and/or
configured to accommodate a single level of specimens 230 to avoid
highly variable upstream and downstream reaction conditions, as in
the prior art apparatus 100 of FIG. 1.
[0014] The inlet port 210 and the module inlets 206 may be aligned
with the longitudinal axis of the reaction chamber 202, as shown
for the exemplary apparatus 200 of FIG. 2. Accordingly, the
conduits 212 may be substantially straight. At least one of the
conduits 212 may pass through at least one of the reaction modules
204 prior to terminating in another of the reaction modules 204.
Also or alternatively, at least one of the conduits 212 may include
bends or curves to accommodate a particular module arrangement
and/or chamber geometry. The conduits 212 may be stiff or flexible.
During operation of the apparatus 200, the conduits 212 may be in
fluid communication with a single gas source or with multiple gas
sources. The outlet port 214 may be aligned with the longitudinal
axis of the reaction chamber in opposition to the inlet port 210,
or the outlet port 214 may have some other placement in the chamber
202. As indicated above, there may be multiple outlet ports 214.
The reaction chamber 202 typically has a cylindrical shape,
although other shapes (e.g., rectangular parallelepiped, sphere,
etc.) are possible. Similarly, the reaction modules 204 typically
have a cylindrical shape but other shapes as indicated above are
also possible.
[0015] Typically, the reaction chamber 202, the reaction modules
204 and/or other components of the apparatus 200 are made of a
refractory material such as graphite or a carbon composite that can
withstand temperatures in excess of 2000.degree. C. and has good
thermal properties and chemical resistance.
[0016] In addition to the apparatus described above, an improved
method of coating specimens using CVI or CVD has been developed.
The method is described in reference to FIG. 2, as the apparatus
200 shown in this figure and described in detail above may be
employed for the method.
[0017] The method includes heating a reaction chamber 202
containing a plurality of specimens (e.g., porous specimens) 230.
The reaction chamber 202 comprises a plurality of reaction modules
204, where each reaction module 204 includes a module inlet 206 and
a module outlet 208 and contains at least one of the porous
specimens 230. In a CVI process, gaseous reagents are flowed
through the module inlets 206 and into the reaction modules 204,
where they infiltrate the porous specimens 230 and chemically react
to form coatings on the porous specimens 230. In a CVD process,
gaseous reagents that flow through the module inlets 206 and into
the reaction modules 204 chemically react to form coatings on the
specimens without necessarily infiltrating the specimens, which may
not be porous. In CVI or CVD, the pressure in each of the reaction
modules 204 is higher than the pressure in the reaction chamber 202
to ensure that gaseous reaction products are expelled from the
reaction modules 204 through the module outlets 208. The gaseous
reaction products may then be removed from the reaction chamber 202
through one or more outlet ports 214. As a consequence, the
reaction products from each reaction module 204 are substantially
prevented from contaminating CVI or CVD reactions occurring in
adjacent reaction modules 204.
[0018] The gaseous reagents may be flowed into the reaction modules
through a plurality of conduits 212 in fluid communication with one
or more gas sources outside the chamber 202, where each conduit 212
terminates in one of the reaction modules 204. Each conduit 212 may
pass through or be connected to one or more inlet ports 210 in the
reaction chamber 202, as described above. Each conduit 212 may pass
through at least one of the module inlets 206. As shown in FIG. 2,
at least one of the conduits 212 may extend through at least one of
the reaction modules 204 prior to terminating in another of the
reaction modules 204.
[0019] The outlet port(s) 214 of the reaction chamber 202 may be in
fluid communication with a vacuum pump. Also or alternatively, the
flow rate of the gaseous reagents into the reaction modules 204 may
be controlled. Thus, a suitable pressure differential between the
reaction chamber 202 and the reaction modules 204 may be achieved
along with forced flow of the gaseous reagents through the reaction
modules 204. The pressure in each of the reaction modules 204 may
be in a range from about one to about five orders of magnitude
higher than that in the reaction chamber 202. In other words, the
pressure may be from about 10 times to about 100,000 times higher
in the reaction modules 204 than in the reaction chamber 202. For
example, the pressure in each of the reaction modules 204 may be in
a range from about 1 Torr to about 50 Torr, and the pressure in the
reaction chamber 202 may be in a range from about 1 mTorr to about
50 mTorr. Typically, the method is carried out with each of the
reaction chamber 202 and the reaction modules 204 at a pressure
below atmospheric pressure (760 Torr). Thus, prior to introducing
the gaseous reagents into the reaction modules 204, the reaction
chamber 202 and the reaction modules 204 may be evacuated to a
desired vacuum level (i.e., to a desired a sub-atmospheric pressure
level) using one or more vacuum pumps.
[0020] Typically, the reaction chamber 202 is heated to an elevated
temperature in a range from about 700.degree. C. to about
1800.degree. C. The heating may comprise inductive heating,
radiative heating, microwave heating, or another heating method
capable of increasing the temperature of the reaction chamber 202
to the desired elevated temperature. The reaction chamber 202 is
maintained at the elevated temperature during the CVI or CVD
process, which may be carried out for a period of 15 minutes to 100
hours.
[0021] The gaseous reagents employed in the process may include a
reaction precursor and a carrier gas and may depend on the coating
to be formed. In one example involving porous specimens, the
specimens to be coated may be fiber preforms comprising silicon
carbide (SiC) and the coating may be a fiber interphase coating
comprising carbon or boron nitride. In another example involving
porous specimens, the specimens to be coated may be SiC fiber
preforms and the coating may be a matrix (or rigidization) coating
comprising SiC. If desired, both a fiber interphase coating and a
matrix coating may be applied to the fiber preform in separate but
sequential CVI processes, which may be carried out as described
above and/or in the apparatus described above. The fiber preforms
that undergo coating may be fabricated using fiber arrangement and
lay-up processes known in the art.
[0022] If a matrix coating comprising SiC is to be formed by CVI on
a SiC fiber preform, the gaseous reagents may include
methyltrichlorosilane (CH.sub.3SiCl.sub.3; reaction precursor) and
hydrogen gas (H.sub.2; carrier gas). During the chemical reaction,
methyltrichlorosilane may decompose to form solid SiC and gaseous
hydrochloric acid (HCl), the former of which is deposited on the
fiber preform as the coating while the latter is removed from the
reaction modules by entrainment in the carrier gas. Other gaseous
reagents (including reaction precursors and carrier gases) suitable
for forming matrix coatings and fiber interphase coatings are known
in the art and may be employed in the above-described method and
apparatus.
[0023] As would be apparent to the skilled artisan, the method
described here may be carried out in the apparatus described above,
including any of the components, configurations, and/or
capabilities shown in FIG. 2 and/or set forth in the above
description.
[0024] As would also be recognized by the skilled artisan, the
above-described apparatus and method may be used to coat specimens
using CVI or CVD. Porous specimens are typically coated by CVI,
whereas the specimens coated by CVD need not be porous. The
apparatus employed for CVD may be similar or identical to the
apparatus employed for CVI. Other aspects of the method and
apparatus described for CVI may apply also to CVD.
[0025] To clarify the use of and to hereby provide notice to the
public, the phrases "at least one of <A>, <B>, . . .
and <N>" or "at least one of <A>, <B>, . . .
<N>, or combinations thereof" or "<A>, <B>, . . .
and/or <N>" are defined by the Applicant in the broadest
sense, superseding any other implied definitions hereinbefore or
hereinafter unless expressly asserted by the Applicant to the
contrary, to mean one or more elements selected from the group
comprising A, B, . . . and N. In other words, the phrases mean any
combination of one or more of the elements A, B, . . . or N
including any one element alone or the one element in combination
with one or more of the other elements which may also include, in
combination, additional elements not listed.
[0026] Although considerable detail with reference to certain
embodiments has been described, other embodiments are possible. The
spirit and scope of the appended claims should not be limited,
therefore, to the description of the preferred embodiments
contained herein. All embodiments that come within the meaning of
the claims, either literally or by equivalence, are intended to be
embraced therein.
[0027] Furthermore, the advantages described above are not
necessarily the only advantages, and it is not necessarily expected
that all of the described advantages will be achieved with every
embodiment.
* * * * *